1. Field of the Invention
The present invention relates to a semiconductor apparatus and a semiconductor device mounting method. More particularly, the present invention relates to a semiconductor apparatus and a semiconductor device mounting method in which a mechanical connection force is improved between a substrate and a semiconductor device.
2. Description of the Related Art
In recent years, the miniaturization of an electronic apparatus has been advanced, and its price has come down. In association with them, a flip-chip method is proposed as a structure in which semiconductor devices are mounted at a high density.
The semiconductor device mounting method in the flip-chip method is the method of connecting a semiconductor device, in which a plurality of bump electrodes are mounted on at least one surface, to a circuit substrate, by performing a face-down on a side on which the bump is mounted.
A conventional flip-chip mounting structure will be described below with reference to FIG. 1.
As shown in FIG. 1, in the conventional flip-chip mounting structure, a mount pad 73 is formed on a circuit substrate 71. A plurality of bumps 74 is formed on the surface of the side of the circuit substrate 71 on a semiconductor device 72. The mount pad 73 is usually produced by copper plating. Nickel-gold plating is coated thereon. Its surface is relatively smooth.
Then, the semiconductor device 72 is mounted on the substrate 71 by connecting the mount pad 73 to the bump 74. The followings are the conventional connecting methods.
As a first method, a gold protruded bump (bump 74) is firstly formed on the semiconductor device 72 by using a wire bonding method. Next, Ag paste is coated on an upper portion of the protruded bump. Then, the protruded bump is pushed against the mount pad 73, and adhered thereto (Journal of Japan Institute for Interconnecting and Packaging Electronic Circuits, Vol. 11, No.5 (1996) P347).
As a second method, the gold protruded bump (bump 74) is firstly formed on the semiconductor device 72 by using the wire bonding method. Then, the protruded bump and the substrate 71 are soldered to each other (Journal of Japan Institute for Interconnecting and Packaging Electronic Circuits, Vol. 11, No.5 (1996) P319).
And, as a third method, the gold protruded bump (bump 74) is firstly formed on the semiconductor device 72 by using the wire bonding method. Next, solder is sent to the mount pad 73. Then, the bump 74 and the mount pad 73 are soldered to each other (Journal of Japan Institute for Interconnecting and Packaging Electronic Circuits, Vol. 11, No.5 (1996) P343).
In all the above-mentioned methods, as shown in FIG. 1, after the semiconductor device 72 is placed on the substrate 71, a seal resin 75 is filled between them. In this configuration, the pad 73 and the bump 74 are integrally bonded over the boundary between them. However, the thermal expansion coefficient of the semiconductor device 72 is different from that of the substrate 71. In particular, it differs from an organic substrate by as much as five times. For this reason, large stress is induced in a connection portion, which may result in an occurrence of a connection defect. Thus, by filling the seal resin 75 between the semiconductor device 72 and the substrate 71, it is necessary to disperse the stress.
A connecting method of using a contraction force of the seal resin 75 will be described below with reference to FIGS. 2A to 2B. At first, the seal resin 75 is placed on the substrate 71 on which the semiconductor device 72 is placed. Next, as shown in FIG. 2B, a position of the semiconductor device 72 is made coincident with that of the mount pad 73 by carrying out the face-down. As shown in FIG. 2C, while the semiconductor device 72 is placed on the substrate 71 and a tip of the bump 74 is deformed under a heating and pressing process, the mount pad 73 and the bump 74 come in direct contact with each other. At that time, until the seal resin 75 is cured, the heating and pressing process is continued to thereby obtain the mechanical electronic connection.
In the above-mentioned methods, the semiconductor device 72 and the substrate 71 are not mechanically fixed until the seal resin 75 is cured. For this reason, it is difficult that immediately after placing the semiconductor device 72 on the substrate 71, it is moved to another apparatus and the heating and pressing process is done in order to shorten an occupation time of the mounted unit.
In view of the above-mentioned circumstances, a semiconductor apparatus having an excellent productivity is desirable in which the mechanical connection force is improved between the substrate 71 and the semiconductor device 72.
As the related technique, Japanese Laid Open Patent Application (JP-A-Heisei 10-50765) discloses a method of mounting a semiconductor device and a technique of a semiconductor apparatus. The semiconductor apparatus based on this technique is formed by mounting the semiconductor device on a substrate. It has a mount pad, a bump electrode and a seal resin. Here, the mount pad is formed on the substrate, and it has a concave and convex portion on the surface thereof. The bump electrode is formed on the surface of the substrate side of the semiconductor device, and it is arranged while it is inserted into the concave and convex portion of the mount pad. The seal resin exists between the semiconductor device and the substrate.
It is described that this technique is used to insert the bump electrode into the concave and convex portion formed on the surface of the mount pad, and the connection strength is improved.
Japanese Laid Open Patent Application (JP-A-Heisei 7-201917) discloses a technique of a circuit formation substrate and a method of manufacturing the same. The circuit formation substrate based on this technique has an electrically insulating substrate, a thin film metallic electrode disposed on a surface of the electrically insulating substrate, and an electronic part electrically connected through a bump to the thin film metallic electrode. Then, a concave and convex layer is formed on the surface of the thin film metallic electrode or the electrically insulating substrate of the ground thereof.
It is described that since the respective bonding conditions (contacts) between the electrically insulating substrate, the thin film metallic electrode and the bump can be made stronger by using this technique, the reliability can be improved.
Japanese Laid Open Patent Application (JP-A-Heisei 10-270498) discloses a technique of a method of manufacturing an electronic apparatus. The electronic apparatus manufacturing method based on this technique includes the steps of: preparing an electronic device in which a solder protrusion electrode is formed on a surface; preparing a wiring substrate in which a needle-like electrode made of a material having a melting point higher than that of a member of the solder protrusion electrode and having a high elastic coefficient is formed on a surface; making a position of the solder protrusion electrode and a position of the needle-like electrode coincide with each other, pushing the needle-like electrode until it reaches a ground electrode of the solder protrusion electrode and carrying out a tentative connection; and performing a re-flow on the solder protrusion electrode and regularly connecting the electronic device and the wiring substrate to each other.
It is described that this technique can shorten the step of manufacturing the electronic apparatus and can also improve the yield of the electronic apparatus.
However, since the semiconductor apparatuses disclosed in the above-mentioned gazette have the concave and convex portion on the surface of the substrate, they are strong against a stress in a flat direction, and weak against a vertical force. This is because their convex portion and needle-like electrode are wide near the side of the surface of the mount pad, the substrate and the electrode, and narrow near their tip side of the convex and the needle. Therefore, they have no substantial resistance against a thermal expansion or an external force in a vertical direction that causes the semiconductor device to be stripped from the substrate. Also, if the concave and convex portion is formed by using sand blast, metallic powder and the like, since it has the basic shape similar to a sphere or a polygon, a sufficiently large particle is needed in order to obtain an effective height as an anchor. For example, if a concave and convex portion having a depth of 5 xcexcm is formed by using the sand blast, a grind stone having a diameter of at least 10 xcexcm is needed. Thus, it is difficult to form the effective concave and convex portion in a narrow pad having a width of approximately several 10 xcexcm.
Therefore, an object of the present invention is to provide a semiconductor apparatus in which a mechanical connection force is improved between a substrate and a semiconductor device
Another object of the present invention is to provide a semiconductor device mounting method having an excellent productivity in which a mechanical connection force is improved between a semiconductor device and a substrate.
Still another object of the present invention is to provide a semiconductor apparatus and a semiconductor device mounting method, which their reliability is improved.
In order to achieve an aspect of the present invention, present invention provide a semiconductor apparatus including a mount pad formed on a substrate and a bump formed on a semiconductor device. In the semiconductor apparatus, a plurality of needle-like or branch-like protrusions is formed on at least one of the mount pad and the bump. The plurality of protrusions of one of the mount pad and the bump engages with the other.
In the semiconductor apparatus, the plurality of protrusions protrudes in directions crossing each other.
In the semiconductor apparatus, the plurality of protrusions protrudes to random directions.
In the semiconductor apparatus, a length of the plurality of protrusions is 5 to 10 xcexcm.
In the semiconductor apparatus, a number of the plurality of protrusions is 100000 to 200000/mm2.
In the semiconductor apparatus, a length of the plurality of protrusions is 10 to 15 xcexcm.
In the semiconductor apparatus, a number of the plurality of protrusions is 50000 to 100000/mm2.
In the semiconductor apparatus, the substrate is produced by one of a full additive process and a sub additive process, and the plurality of protrusions is formed only on a side of the semiconductor device of the mount pad.
In the semiconductor apparatus, the plurality of protrusions is coated with Au.
In the semiconductor apparatus, the bump includes Au.
In the semiconductor apparatus, the mount pad includes Au.
In the semiconductor apparatus, the protrusions are coated with a low temperature brazing filler metal of non-lead system.
In the semiconductor apparatus, the plurality of protrusions is formed by a plating method.
In the semiconductor apparatus, seal resin is filled between the semiconductor device and the substrate.
In order to achieve another aspect of the present invention, present invention provide a semiconductor device mounting method including the steps of (a) forming a plurality of needle-like or branch-like protrusions on a surface of at least one of a mount pad formed on a substrate and a bump formed on a semiconductor device; and (b) positioning the semiconductor device on the substrate such that the bump faces the mount pad and the plurality of protrusions of one of the mount pad and the bump engages with the other.
In the semiconductor device mounting method, the (b) positioning step includes the step of (c) pressing the semiconductor device on the substrate.
In the semiconductor device mounting method, the (c) pressing step includes the step of (d) heating the semiconductor device and the substrate at temperature sufficient to form contact between the bump and the mount pad.
In the semiconductor device mounting method, the (a) forming step uses a plating method for forming the plurality of protrusions.
In the semiconductor device mounting method, the (a) forming step includes the step of (e) supplying seal resin onto the substrate, and the (b) positioning step includes the step of (f) curing the seal resin.
In the semiconductor device mounting method, the seal resin is cured by a unit different from a unit placing the semiconductor device on the substrate.